Solid state TV pickups, for example CCD's (Charge Couples Devices) or CID's (Charge Injection Devices) are presently available only for the American television "NTSC" standard as regards the number of lines and frames.
In order to use these solid state TV pickups for the CCIR standard having 625 lines, it would be possible to omit a suitable number of lines at the upper and at the lower picture margin, respectively. Since the number of visible lines in a frame according to the American standard is 487, whereas the corresponding number for a frame is 575 in the CCIR standard, 44 lines would be missing at each of the upper and the lower picture margins in the full frame, i.e., 22 lines in each field.
In order to preserve the overall image ratio of 4:3, it is necessary to perform a reduction and lateral redistribution of the picture dots in each line, which results in corresponding black margins at the picture sides. Altogether, the resulting picture would be 15% smaller in each its dimensions and would thus be unsatisfactory.